Preheat your oven to 350, and line two baking sheets either with parchment paper or silpats.

In either a large metal bowl or a stand mixer, whisk together the flour, salt, and baking powder. While you can certainly bring this dough together by hand, it will require some vigorous stirring, so I would advise bringing out the big guns for this one if you've got 'em.

Meanwhile, combine the margarine, sugar, and corn syrup in a small saucepan and set over medium-low heat. Gently cook the mixture and stir occasionally, just until the margarine has melted and the sugar granules have dissolved. Pour the hot liquid into the bowl of dry ingredients, and mix well. It will become very thick and hard to mix, but give it all you've got and make haste- It will become only stiffer as it cools.

Turn out the smooth dough onto a lightly floured surface, press it into a ball, and roll it out to about an 1/8-inch in thickness. Cut it into your desired shapes with cookie cutters and transfer the cookies over to your prepared baking sheets. Sprinkle with colored sugar or sprinkles as desired, and lightly press the decorations in with the palm of your hand.

Bake each sheet individually for 8 - 15 minutes, depending on the size of your cookies. You should be looking for the barest amount of browning on the edges, but nothing that's fully golden brown. Let the cookies sit for a minute before moving them over to a wire rack to cool.